Harvesting is an important step in the wood processing chain, creating a basis for the profitable wood processing chain from the forest to the client. A wood procurement organization is responsible for deliveries of raw material to factories, that is, production plants, and of fuel to combustion plants. A raw material purchase order is based on the demand of end products. Wood raw material is delivered according to purchase orders, with respect to the date of delivery, quantity and quality. An object in the planning of harvesting is that a correct quantity of the wood raw material needed can be delivered at the right time. The operation is determined by a procurement plan according to the raw material purchase orders of the production plants. The annual procurement plan is expanded in a plan for a few months, for example.
Roadside storages must contain a quantity of timber assortments complying with transportation plans at agreed time. By controlling the harvesting, the storages are kept in desired size and the ratio of timber assortments in them is kept to best correspond the situation at each time. A smooth flow of information is a requirement for successful operation. For the control, data systems are applied in such a way that a flexible supply of raw material becomes possible.
From the available resources or reserves of stands marked for cutting, suitable stands and ranges are selected for harvesting. Seasonal variation has a strong effect on the harvesting, which is particularly difficult in seasons of impassable road conditions.
Sources of raw material include forests owned by e.g. forest companies, corporations, and private persons. In a timber sale contract, an agreement is made on the timber assortments to be harvested and their quantities, and also on the harvesting of fuel wood, if necessary. In sale at delivered price, the seller commits himself to deliver the agreed quantity and assortment of timber to the delivery point at the agreed time. In sale of standing timber, the buyer takes care of the felling of the quantity and assortment of timber as the object of purchase, and its transportation from the forest. Timber assortments include, among other things, pine log, pine pulpwood, spruce log, spruce veneer log, spruce pulpwood, birch log, birch pulpwood, other logs, other pulpwood, and wood fuel, such as stumps and logging residue.
Timber is supplied to a production plant or a combustion plant from several different sources, wherein purchases for delivery to a mill yard, purchases for delivery to a roadside storage, as well as harvesting by the plant's own organization, and other procurement of wood are feasible. The wood raw material is typically delivered to the buyer from several different sources based on a transportation plan, and timber is delivered to the buyer from stands marked for cutting and harvesting, from roadside storages used as delivery points, and from timber terminals.
By utilizing data systems, the data of a stand ready for harvesting are trans-ferred from the party responsible for logistics to the forest machine company, even directly to a harvesting machine, and the logging contractor is responsible for the harvesting. The data of ready timber are transferred to the data system of the wood procurement organization, and the transportation plan is drawn up on the basis of the data received.
In the planning of the stand marked for cutting, data is produced for planning the harvesting. It determines, for example, the accumulated quantity of timber from the stand marked for cutting, and if necessary, the stand is divided into ranges to be harvested. In the planning of harvesting, the locations of roads and storage points are also determined. Factors affecting the scheduling of the harvesting of the marked stand and the range to be harvested include the wood demand of the processing plants and the reserve of stands marked for cutting, as well as the bearing capacity of the stands marked for cutting and of the roads to be used. The equipment will be selected on the basis of the felling method, the heaviness of the standing timber to be felled, the time of harvesting, and other site condition factors. The harvesting method applied is typically cut-to-length (CTL) logging with a chain of machines consisting of a harvester and a forwarder.
For the marked stand and the range to be harvested, harvestability and transportability as well as possible time of harvesting are also defined. For example on peaty soils, poor bearing capacity of the soil must be taken into account for the harvesters and forwarders. Harvesting of peaty soils predominated by spruce is performed when the soil is frozen, to avoid damage to the roots. In a forest stand predominated by pine, harvesting is also possible when the soil is unfrozen. For peaty soils with good drying conditions, the harvesting and transportation conditions in the summer may be almost the same as for mineral soil.
According to the prior art, the stand marked for cutting can also be planned automatically in advance. For stocktaking of forest resources, remote sensing methods are also used, in which, for example, airborne laser scanning (ALS) and aerial photographs are applied. By means of the methods, the data obtained can be used for automatic determining of standing timber patterns, that is, homogeneous areas with similar dominant tree species and growing stock density. An analysis based on laser scanning will also produce data on the standing timber with respect to the tree species and length, and by means of modelling, data can even be obtained on the diameter and volume of trees. Laser scanning will also produce a topographical model of the terrain, which information can be utilized for planning the harvesting, particularly for determining the transportability. The stands marked for cutting are formed automatically, and, for example, thinning or final cutting is selected. On the basis of the data, it is also possible to conclude the quantity and assortment of timber to be obtained from the stand. The data can be updated or checked by means of a field inspection when needed.
In planning the harvesting, not only automatic allocation of stands to be marked for cutting is used, but also data on the road network in the form of geographic information and typically also the road classification. In harvesting, the road network also forms passage obstacles, but the data on the road network can also be utilized for selecting a location for a roadside storage. Passage obstacles are also formed by water systems, on which data is obtained in the form of geographic information for planning the harvesting. Terrain contour lines are also available in the form of geographic information. Briefly defined, geographic information (GI) is information with a position. The data to be described is so-called property information. Geographic information is produced, for example, by soil investigating organizations.
In a data system, it is thus possible, on the basis of remote sensing and geographic information according to prior art, to plan both the stands to be marked for cutting and the location of roadside storage points, and also to lay out the transportation routes from the stand to the storage point, taking into account the limitations set by the terrain and the environment. In practice, the transportation is implemented by means of forwarders, so that on the basis of a topographical model it is possible to lay out the transportation routes to locations passable for a forwarder, taking into account, for example, the tilt angles.
Data on the soil type is also available in the form of geographic information, on the basis of which it is possible to define the primary soil type of the stand to be marked and the range for harvesting. The soil types include, for example, mineral soil types and organic soil types. The soil type is further specified with additional attributes which indicate how the soil types deviate from their basic type. The mineral soil types include, for example, boulder soil and cobbly soil, gravel soil, morainic soil, sandy soil, fine-sand soil, silty soil, and clay soil. The organic soil types include, for example, slimy and muddy soil, as well as humus soil, consisting of top soil or peaty soil type.
In harvesting, a temporal description which is partly based on the seasons is used for determining harvestability and transportability. For the mineral soil types, the bearing capacity of the terrain varies to a great extent, so that the bearing capacity plays an important role in determining the harvestability. Forests on peaty soils are almost always classified to be harvested in the winter, although there is great variation. Furthermore, it should be noted that the amount of growing stock also affects the bearing capacity of the terrain, particularly because of the amount of rootage. When the bearing capacity of the soil is sufficient, the soil can bear the weight of the harvester and particularly the forwarder carrying a load of timber.
Conventionally, stands marked for cutting are divided into three different classes according to harvestability. In stands marked for cutting during the season of frost damaged roads, timber can be harvested and transported at any time, even during the seasons of poor road conditions in the spring and in the autumn. In stands marked for cutting in the summer, timber can be harvested and transported at other times than in the spring and in the autumn when the roads are impassable. In stands marked for cutting in the winter, harvesting and transportation is only possible when the soil is frozen. The classification can also be selected in another way; for example, stands which can be harvested when the soil is unfrozen are divided into subclasses, and, for example, harvesting and transportation are possible provided that there is low autumn rainfall even if the summer was rainy, or during a dry summer only.
The primary soil type of the stand marked for cutting and the range to be harvested, as well as the soil type of the transportation routes, can be obtained by utilizing e.g. geographic information. The harvestability and the transportability can be concluded, for example, on the basis of certain rules or experience. In the prior art, the primary soil type has determined the times when harvesting is not possible or is possible but at varying costs. Information on the costs of harvesting at different times of harvesting, the possible transportation routes at different times of harvesting, the costs of transportation caused by different transportation routes, the numbers of visits to the stand or the range to be harvested, and the quantities and assortment of timber to be obtained from the stand is used in the prior art for calculating the harvesting costs at different times of harvesting. On the basis of this data, it is possible to make the desired optimization, to find out, for example, the optimal harvesting time in view of the costs.
The selection and optimization of transportation routes according to the prior art, based on the planning of the stand, is discussed in the document Koljonen, Juha-Matti et al: Mat-2.4177 Operaatiotutkimuksen projektityöseminaari: 4. Puustokuvion korjuukelpoisuus ja saavutettavuusanalyysi [Project work seminar on operation research: 4. Analysis on Harvestability and Accessibility of Standing Timber Pattern] (University of Technology, Department of Information and Natural Sciences; Project work; Espoo, 20 Apr. 2009).
However, in view of harvestability and transportability, said classification based on geographical information and derived from it is insufficient or is not sufficiently accurate for planning the harvesting. Significant annual variations may occur in the environmental conditions, for example in view of the onset and depth of soil frost, the quantity of snow, and also the amount of rainfall. The classification according to the prior art may lead to the harvesting of a marked stand for example only when the soil is frozen, although a more accurate inspection would show that it would also be possible in the summer. Similarly, the definition of harvestability and transportability is usually made in connection with the timber sale contract and the field inspection, wherein the assessment may be incorrect or insufficient so that harvesting is no longer possible because the bearing capacity of the soil has changed as a result of raining. The classification can be specified by adding further classes, but the planning of harvesting still lacks information on whether the real harvestability and transportability of, for example, a stand marked for cutting, for example its bearing capacity or an index describing it, corresponds to the value defined on the basis of, for example, geographic information on the soil type of the ground.
It is true that the classification can be improved by means of geographic information, but the definition of the harvestability and transportability is still not on a sufficiently accurate level so that the whole wood processing chain would operate optimally and could provide the deliveries of wood raw material in a reliable way and on the basis of exact data. Inaccurate and incorrect data constitute an unnecessary burden on the whole wood processing chain.